Alloy



'sisting of vanadium,

United States Patent ALLOY Clyde J. Welcker, New Orleans, La., assignor, by mesne assignments, to Butler Engineering Company, Inc., New Orleans, La.

No Drawing. Application February 28, 1951, Serial No. 213,280

8 Claims. (Cl. 204-149) This invention relates to an alloy, and more particularly to an alloy of zinc and one of the metals selected from the group consisting of vanadium, molybdenum and tungsten. Additionally, the alloy may contain aluminum or magnesium, or both aluminum and magnesium, in small amounts that are effective to aid in the formation of the principal alloy consisting essentially of zinc and one of the metals selected from the group named, or mixtures of such selected metals.

While the alloy of my invention has many uses, such as'for structural purposes and in the form of die cast articles and parts, it will be herein described principally in connection with its use as an anode in an electrolytic water correction device, wherein the anode is used in conjunction with a cathode, which may have a surface of a metal or alloy, such as iron, copper or silver, standing lower than zinc in the electromotive series of the metals; that is the cathode is formed of a positive metal such as copper or the like while the anode is formed from a negative metal such as zinc. The galvanic action of such a self-energizing electrolytic water correction device and its mode of operation in eliminating or reducing the formation of a hard scale in water systems used for the generation of steam, for heating purposes or in the cooling systems of internal combustion engines, are explained in many of the patents to Edgar M. Butler, including the Butler Patents Nos. 2,424,145; 2,451,064; 2,451,065; 2,451,066; 2,451,067 and 2,451,068.

The alloy of my present invention has many advantages in connection with its use as an anode in an electrolytic water correction device in place of the zinc anode employed in the devices described in the above listed Butler patents. Among these advantages are: increase in the activity of the anode at low water temperatures; increase in the area of the anode that is made efiective during the life of the anode in use; dispersal into the water of substances that more eifectively prevent the formation of a hard silica scale; and dispersal of a substance that also inhibits the corrosion of both iron and copper.

The principal ingredient that I alloy with zinc in forming the alloy of my invention is a polyvalent metal capable of forming an anion, and is selected from the group conmolybdenum and tungsten, or a mixture of any two or all of these members of the group. The problem is to alloy one or more of these high melting point metals with such a low melting point metal as zinc. I have, however, been able to solve this problem and to provide an alloy containing from 0.01 to 1.0% by weight of one or more of these selected metals, with the balance being substantially all zinc, except that where a percentage of the selected metal within the higher portion of the range is desired, it is preferable to use from 0.25 to 7% of aluminum and from 0.05 to 0.5% of magnesium to assist in forming the alloy of zinc and the selected group metal.

It is therefore an important object of this invention to provide an alloy of zinc and one or more of the metals: vanadium, molybdenum and tungsten.

It is a further important object of this invention to provide a cast alloy that is useful as the anode of an electrolytic water correction device and that has many advantages over the use of zinc, alone, for the same purpose. Other and further important objects of this invention will become apparent from the following description and appended claims.

In preparing the alloy of my invention, I have found that it is preferable to have the principal alloying ingredi- 2,700,647 Patented Jan. 25, 1955 ent, or ingredients in a finely granular state so as to present greater surface areas and, therefore, provide for faster alloying with the zinc. The alloying ingredients that I employ are vanadium, molybdenum or tungsten, or mixtures of two or more of these metals. In order to assist in the formation of the alloy, I find it desirable to use small quantities of aluminum, or magnesium, or both. The magnesium serves as a de-oxidizing' agent in the preliminary melting of the alloying ingredients, and serves primarily to prevent oxidation of the polyvalent alloying metals before they have an opportunity to alloy with the zinc. Also, a slight amount of magnesium is beneficial as it aids in formation of a better crystalline structure of alloy and also aids by increasing the rate of corrosion of the anode where the alloy is used as an anode in electrolytic water correction devices.

In making the alloy, according to my preferred method the aluminum is melted first and then vanadium, molybdenum or tungsten, or a mixture of these alloying ingredients, is added to the molten aluminum. The alloying ingredient selected is added in a granular, or particle state, preferably of a particle size less than inch in maximum dimension. Preferably magnesium of smaller particle size than the alloying ingredient is mechanically admixed with the alloying ingredient and the resulting mixture is added to the melt. The magesium is of much smaller particle size than that of the alloying ingredient, so that the magnesium may be spread out evenly over the entire cross-section of the molten mass. If the magnesium is used in large pieces it is immediately submerged, by means of tongs, or the like, beneath the surface of the melt, as it is added, in order to minimize oxidation and possibly ignition of the magnesium before it has been distributed through the melt. The magnesium then serves to prevent undue oxidation of the vanadium, molybdenum or tungsten.

Zinc is next added to the melt in small portions, adding the zinc slowly either as a solid or in molten state. The volume of the molten mass is thus increased slowly, with the result that a longer melting time is provided for a. better diffusion of the ingredients and alloying therebetween.

The order of addition of the metals to the melting crucible, or mold, is important not only to achieve certain definite crystalline characteristics but also to control melting and pouring temperature of the final alloy. The sequence of additions just described avoids excessively high temperatures to effect alloying, and thus avoids excessive vaporization of the lower melting point metals, such as zinc, and alsoavoids oxidation of the zinc.

According to a modified procedure, the alloying ingredient, vanadium, molybdenum, or tungsten, is positioned in the bottom of the crucible and covered with molten aluminum, or the aluminum is melted in the crucible on top of the polyvalent alloying ingredient. After being allowed to stand for awhile, the mass is stirred to elfect alloying. It has been found that alloying takes place more readily if the mixture is allowed to stand for 10 or 15 minutes before stirring. The magnesium in the amount desired to be alloyed is then added in rather large pieces, which are immediately submerged beneath the surface of the molten aluminum, with stirring. Zinc is then added, as in the procedure previously set forth. A carbide crucible, preferably one that has been glazed by prior melting of alloys containing silicon, is not readily attacked by the polyvalent alloying metal.

The broader range of the alloying ingredients is from 0.01 to 1.0% of the metal selected from the group consisting of vanadium, molybdenum and tungsten, and mixtures of two or all of these alloying metals, with the balance being substantially zinc. A narrower, preferred range is from 0.05 to 0.36% of the polyvalent alloying metal, with the balance substantially all zinc, except for some small percentage of aluminum and magnesium. In order to increase the percentage of the metal, or metals, selected from the group just defined, above about 0.20%, and up to a total of 1% by weight, it is preferable to add aluminum or magnesium, or both aluminum and magnesium, as above described. Thus, where a percentage of the selected metal from the group mentioned is to be in the higher range, approaching a total of 1.0%,

corroded as to, have too short'a life in the boiler.

it i'spreferable to usefrorn 0.25 to 7% of aluminum and from 0.05 to 0.5% of magnesium. All percentages are, of course, given in parts by weight. Whether the alloy comprises zinc and a polyvalent metal selected from the group defined, or, in addition, aluminum and magnesium, the alloy exists as a homogeneous .phase when prepared in accordance with my invention.

More specifically, where the percentage of the se- 'lected alloying metal, or metals, selected lfromthe above defined group is not to exceed 0.18% by weight of the alloy, it is not necessary to add aluminum and mag- 'nesium, or either of them, to themelt, but it is still preferable to add either aluminum or magnesium, or both, in order to decrease the time required for effecting the formation of the alloy. Part of the magnesium'initially added is usually oxidized and thus 'not all of the magnesium added is present in the final alloy.

The final alloy is, then, essentially an alloy of zinc and from0.'0l 'to 1.0% of a metal, or' mixture of metals, selected fromthe group consisting of vanadium, molybdenum and tungsten. M

The activity of the zinc when used in an electrolytic water correction method is increased with any slight addition, say 0.01% or over, of any of the polyvalent metals, vanadium, molybdenum or tungsten. For water correction purposes, any one of these metals is suitable.

Where the alloy is one of zinc and vanadium only, the alloy is workable and sustains considerable cold working before failure occurs. Therefore, where such features as high density, distorted crystalline structure and laminar non-interlocking crystal edges are required, an alloy consisting of zinc and vanadium that has been cold worked is preferred.

. An alloy of zinc and from 0.05 to 0.36% of vanadium can be satisfactorily rolled from east ingot form at a temperature of between 350 to 400 F., at which temperature it is more plastic than when cold. A considerable amount of reduction in cross-sectional area results in distortion and final orientation of the crystals in a longitudinal direction.

Where the alloy consists essentially of zinc and two or all three of the group metals, along with aluminum and magnesium, the original crystalline structure is well defined and rather large. The material is brittle and is notreadily capable of being cold worked. The crystalline structure is dendritic, with crystal growth and crystal faces extending deep into the center of the casting.

Both the alloys that contain only the zinc and one or more of the group metals, and also the alloyscontaining, in addition, aluminum and magnesium, are comparatively hard and give a bell-like tone, when struck. Where corrosion is not a problem, the alloys have many uses in the manufacture of structural parts and die-cast articles. As already pointed out, where the alloys are used in electrolytic water correction devices, their rapid rate of corrosion at relatively low temperatures is an important factor in rendering such devices more effective in low temperature water systems, such as the domestic hot water systems and the cooling systems for automotive and stationary internal combustion engines.

From the stand point of its use as a negative anode 'inan electrolytic water correction device, the alloy is benefited by the incorporation of aluminum into .it. The aluminum causes an excessively large crystal growth, which is advantageous to more rapid and extensive galvanic action. The crystals are inter-locking and dendritic in character, with the edges of the crystals extending inwardly to the center of the casting. This is significant for the reason that it brings the centers of activity closer together, and since the activity is greater on the crystal faces, corrosion will be progressive and more rapid as it proceeds inwardly toward the center. The cast alloy is thus the preferred form for use in electrolytic water correction devices where the temperature of the water system is relatively low, as for instance below the boiling point of water.

Where, however, extremely high water temperatures are present, such as is the case in steam boilers, the rolled form of the alloy is most suitable, since that form is suifi'ciently active galvanically and yet not sofrapidly As aresult of cold rolling, with considerable reduction in cross-section, the grain of the casting is distorted in the direction of the rolling force and a laminar structure results. In the case of water of high silica content,fthe

corrosion of the alloy as the negative element of the water correction device leads to .the formtaion of. complexes of the silica with the anionforming metal of the alloy. Each of the metals, vanadium, molybdenum and tungsten, forms complexes with silica, wherein the silica is completely surrounded by the polyvalent alloying metal, or its anion, with "the result that the continuous chain of silica atoms is interrupted and the silica is not in such a state as to form a hard scale when precipitated out of solution. If precipitation does occur, the silica complex comes out as 'asoft sludge that is comparatively easy of removal from the system.

The polyvalent alloying metal selected also actively forms complexes with iron and particularly the trivalent ferric ion. The presence of a small amount of the polyvalent alloying metal, or its anion, in the water interface at the surface of the iron metal of the container, or vessel, results in the formation of a complex with any iron ions leaving such surface. Concentrations of between 1 and 30 parts per million of the polyvalent alloying metal result in the passivation of the iron, thereby greatly inhibiting corrosion of the iron.

I claim as my invention:

1. In an electrolytic water correction device:including an anode and a cathode, the anode comprising an alloy consisting essentially of zinc, from 0.25 to 7% of aluminum, from 0.05 to 0.50% of magnesium and a polyvalent metal capable of forming an anion and selected from the group consisting of vanadium, molybdenum, and mixtures thereof, said selected metal being present in an amount equal to from 0.01 to 1% by'weight of the alloy.

2. In an electrolytic water correction device constituted by an anode and a cathode, the anode comprising an alloy consisting essentiallyof zinc, from 0.25 to 7% of aluminum, from 0.05 to 0.50% of magnesium and from 0.05 to 0.36% of vanadium by weight of said alloy.

3. A process for electrolytically conditioning water which comprises subjecting the water to be conditioned to the electrolytic action of a self-energizing galvanic couple immersed therein comprising a cathode of ametal lower than zinc in the electromotive series of metals and an anode of an alloy consisting essentially of from about 0.25 to 7% by weight of aluminum, from about 0.05 .to 0.50% 'by weight of magnesium and from about 0.01 to 1% by weight of a polyvalent metal capable of forming an anion selected from the group consisting of vanadium, molybdenum, and mixtures thereof, the balance of said alloy being principally Zinc.

4. In an electrolytic water correction device constituted by an anode and a cathode, the anode comprising an alloy consisting essentially of zinc, from 0.25 to 7% of aluminum, from 0.05 to 0.50% of magnesium and ffiam 0205 to 0.36% of molybdenum by weight of said a oy.

'5.'In .an electrolytic water correction device constituted by an anode anda cathode, the-anode comprising an alloy consisting essentially of zinc, from 0.25 to 7% of aluminum, from 0.05 to 0.50% of magnesium, from 0.0 5 to 0.36% of molybdenum andv from 0.05 to 0.36% of vanadium by weight of said alloy.

, 6. A process for electrolytically conditioning water which comprises subjecting the water to be conditioned to the electrolytic action of a self-energizing galvanic couple immersed therein comprising a cathode ofa metal lower than zinc in the electromotive series of metals and an anode of'an alloy consisting essentially of from about 025 to 7% by weight of aluminum, from about 0.25 to 0.50% by weight of magnesium and from about 0.05 .to 0.36% by weight of vanadium, the balance of said alloy being principally zinc.

7. A process for electrolytically conditioning water which comprises subjecting the water robe conditioned to the electrolytic action of a self-energizing galvanic coupleimmersed therein comprising a cathode of a metal lower than zinc in the electromotive series of metals and an anode of an alloyconsisting essentially of from about 0.25 to 7% by weight of aluminum, from about 0.05 to 0.50% by weight. of magnesium and "from about 0.05 .to 0.36% 'by weight .of molybdenum, the balance ofcsaid alloy:being principally .zinc.

A processfor electrolytically conditioning water which comprises subjecting the water .to be conditioned to "the electrolytic action of a self-energizing galvanic couple immersed therein comprising .a cathode vof-ame'tal lowerlthanizinc in. the. eleetromotive series of metals and by weight of molybdenum, the balance of said alloy being 5 2,451,066

principally zinc.

References Cited in the file of this patent UNITED STATES PATENTS 1,703,577 Falkenberg Feb. 26, 1929 1,850,419 Schroeder Mar. 22, 1932 2,013,870 Starmann Sept. 10, 1935 6 Westbrook May 18, 1937 Schulze May 27, 1941 Daesen Apr. 20, 1943 Bunn Jan. 8, 1946 Butler Oct. 12, 1948 FOREIGN PATENTS Germany Dec. 16, 1916 Great Britain Dec. 7, 1931 France Mar. 21, 1938 OTHER REFERENCES Materials and Methods, October 1950, page 91. 

1. IN AN ELECTROLYTIC WATER CORRECTION DEVICE INCLUDING AN ANODE AND A CATHODE, THE ANODE COMPRISING AN ALLOY CONSISTING ESSENTIALLY OF ZINC, FROM 0.25 TO 7% OF ALUMINUM, FROM 0.05 TO 0.50% OF MAGNESIUM AND A POLYVALENT METAL CAPABLE OF FORMING AN ANION AND SELECTED FROM THE GROUP CONSISTING OF VANADIUM, MOLYBDENUM, AND MIXTURES THEREOF, SAID SELECTED METAL BEING PRESENT IN AN AMOUNT EQUAL TO FROM 0.01 TO 1% BY WEIGHT OF THE ALLOY. 